Performance of Air-O-Cell, Burkard, and Button samplers for total enumeration of airborne spores

Performance of three devices used for the total enumeration of airborne spo res-the Air-O-Cell sampling cassette, the Burkard personal volumetric air s ampler, and the Button Aerosol Sampler-was evaluated under controlled labor atory conditions. The first two are glass-slide impacters; the third collec ts spores on a filter. The samplers were challenged with 0.44-5.10 mum poly styrene latex particles and five microorganisms of 0.84-3.07 mum mean aerod ynamic diameter: Streptomyces albus, Bacillus subtilis, Cladosporium clados porioides, Penicillium brevicompactum, and Penicillium melinii. An optical particle counter measured the particle concentrations upstream and downstre am of each sampler, and thus determined the physical collection efficiency of the three samplers. Collection efficiency of the Button Aerosol Sampler was close to 100% for the entire particle size range studied. The cut-off s ize of each impactor was 2.3-2.4 mum. Acridine orange (with epifluorescent microscopy) and lactophenol cotton blue (with bright light microscopy) stai ning techniques were used for the microscopic enumeration of spores. No sig nificant difference in microscopic counts was found (at the 95% significanc e level) when using these two techniques with the Button Aerosol Sampler fi lters. When the lactophenol cotton blue staining was used to compare total microbial counts yielded by all three samplers, the Button Sampler showed s ignificantly higher counts for the smaller size microorganisms (B. subtilis and C. cladosporioides). For the larger microorganisms (P. brevicompactum and P. melinii) all three samplers yielded similar results. Uniformity of p article deposition on the collection surface was highest for the Button Aer osol Sampler due to the design of its inlet. Thus, the filter collection me thod used with the Button Aerosol Sampler is suitable and can be advantageo us for the enumeration of total airborne spores.